SMART ELECTRONIC SWITCH FOR LOW-POWER LOADS

摘要

A two-wire smart load control device, such as an electronic switch, for controlling the power delivered from a power source to an electrical load comprises a relay for conducting a load current through the load and an in-line power supply coupled in series with the relay for generating a supply voltage across a capacitor when the relay is conductive. The power supply controls when the capacitor charges asynclironously with respect to the frequency of the source. The capacitor conducts the load current for at least a portion of a line cycle of the source when the relay is conductive. The load control device also comprises a bidirectional semiconductor switch, which is controlled to minimize the inrush current conducted through the relay. The bidirectional semiconductor switch is rendered conductive in response to an over-current condition in the capacitor of the power supply, and the relay is rendered non-conductive in response to an over-temperature condition in the power supply.